三向土工格栅变形及筋土界面特性试验研究

为探讨三向土工格栅的筋土界面特性，以三向土工格栅为研究对象，考虑0和90两种拉拔方向（分别记为TX_0工况和TX_90工况）的影响，开展了一系列室内拉拔试验。通过对格栅试样沿拉拔方向4个断面的位移进行监测，研究了三向土工格栅的拉拔力-拉拔位移关系、分段变形特性、三向土工格栅的筋土界面剪胀（缩）特性、平均摩阻力-相对位移特征以及拉拔方向对筋土界面强度参数的影响。研究结果表明:填砂压实度对三向土工格栅拉拔力和筋土界面剪胀（缩）特性的影响显著；法向应力越高，筋土界面剪缩性越大，而剪胀性越小，达到最大剪缩（胀）量所需的剪切位移也越大；筋土界面摩阻力的发挥是一个渐进的过程，呈弹塑性-软化特征；法向应力高于20kPa时，TX_0工况的筋土界面强度较TX_90工况更高。 

Experimental Investigation of Deformation and Geogrid-Soil Interface Behavior of Triaxial Geogrid

In order to investigate the behavior of geogrid-soil interface of traxial geogrid, a series of laboratory pullout tests focusing on triaxial geogrid were conducted considering the effect of two kinds of pullout directions, referred to as TX_0 case and TX_90 case, respectively. The geogrid displacements were measured at four sections along the geogrid specimens. Based on the measurements, the relation between pullout force and pullout displacement and the deformation of each geogrid segment were studied. Furthermore, the dilatancy/shrinkage behavior, the relation between the average friction and relative displacement, and the effect of pullout directions on the interface strength were also analyzed. The experimental results demonstrate that the degree of compaction has a great influence on the pullout force and shear dilatancy/shrinkage behavior of the geogrid-soil interface. As the normal stress increases, the shear shrinkage increases while the shear dilatancy decreases. The shear displacements corresponding to the maximum shear dilatancy/shrinkage also increase with the increase of normal stress. The interface friction develops in a progressive mode and an elasto-plastic softening characteristic is observed of the interface behavior. The geogrid-soil interface strength of the TX_0 case is higher than that of the TX_90 case when the normal stress is higher than 20 kPa.